Embodiments relate generally to heating, ventilation and air conditioning systems, and in particular to humidity control for air conditioning systems.
Packaged, unitary rooftop equipment suffers from energy, humidity, and comfort issues due to the cycling behavior of a compressor and the need to provide outside, or makeup, air continuously. When running at part load, the compressor cycles on and off in response to the thermostat set point and an associated dead band. At the beginning of each cooling cycle, there are several minutes while the evaporator coil is being re-cooled to the supply air delivery temperature and it remains warmer than the dew point of the evaporator entering air and consequently humidity is not removed from the air and condensate does not appear. This leads to some sensible cooling, but no latent cooling (e.g., moisture removal). At the end of each cooling cycle, it takes several minutes for the condensed water film on the evaporator coil to drain down. During this time, the airflow for ventilation re-evaporates the water just condensed on the evaporator coil back into the airstream, rehumidifying the supply air and wasting energy. The combination of these effects leads to less dehumidification of the conditioned area than otherwise would be possible.